I've said 'I am 11 years old' however, I'm 21 years old. How is that possible?

Question

I've been drawn by the artists these days, and of old;
Yet I'm seen only when all around me is cold.

For most of the time you just live and ignore me;
Then you gasp for me, stop for me, mutter below me.

You might say, in surprise, I've been taken away,
But it's true I've been with you, at least 'til today.

When I leave you, you leave too!

Who am I?

Answer 1

Because I was born 10 years BC, then 10 + 11 = 21